Semiconductor devices are used in a variety of electronic and other applications. Semiconductor devices comprise, among other things, integrated circuits or discrete devices that are formed on semiconductor wafers by depositing one or more types of thin films of material over the semiconductor wafers, and patterning the thin films of material to form the integrated circuits.
After fabricating various devices within a semiconductor substrate, these devices are interconnected through metal interconnects. Metal interconnects are formed over the device regions and are formed in multiple layers or levels called metallization levels. Metal interconnects were made of aluminum in traditional processes.
Technology scaling has required aggressively reducing the thicknesses of the metal interconnects in the lower metallization levels. The reduced thicknesses resulted in increased resistances of these metal lines. As a consequence, lower levels of metallization have been replaced by copper, which has a lower resistance.
Additionally, power devices have additional requirements. The current drawn through the pads is significantly higher in power devices. Such pads have to be thicker to improve heat dissipation and heat capacity. This increases the complexity of integrating thick copper into the uppermost metallization level.